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HDX Revelations from the iFixit Teardown

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Initial post: Oct 15, 2013 9:30:57 AM PDT
Last edited by the author on Oct 15, 2013 9:31:31 AM PDT
iFixit posted thier teardown of the Kindle Fire HDX 7" this morning. I have gone step by step and gathered my thoughts on the teardown, in the hopes they might explain some of the new news and/or technical bits for those eagerly awaiting their new HDX.

* Amazon clearly partnered with Qualcomm's early access program for the snapdragon 800 to produce the HDX as a "release wave" device, which makes sense given they would need expertise from the chip vendor to minimize how much skills updates the lab team would need to make. Most of the power management and basic system set of ICs is nearly identical to the reference dragonboard development kit. Also clear from the ecosystem of chips in this device is that Amazon partnered with LG on key aspects of the display and things like the battery charging system. In many ways the architecture of this device, is an LG G2 in a larger form factor, mated to Amazon's ecosystem.

* The level of repairability with the HDX is far inferior to prior versions of the Kindle Fire. This is due mainly to the form factor. As you work to put all of these components in close proximity, reducing weight and thickness, one of the trade-offs is that you begin having to very closely "layer" the components together. What the teardown shows is a lot of adhesive used.

Practical implications:
- Break the screen and it very quickly becomes impractical to repair. Replace the device.

- Amazon appears to have gone overboard to make the internals on this device tough. Our complaints about stuff coming loose like the charging port means that Amazon has used screws, adhesive, and even the way things are layered to try and make the internals tougher. The downside this creates is individual components become hard to work with.

* Amazon has used a higher end charging chip (the SMB349) in the HDX. The neat thing about this is that Amazon can update the firmware on it, it can be programmed to function more efficiently.

- Amazon can "fix" problems discovered with how the device charges later via system updates.

- Amazon can potentially enable the kindle to output from its own battery to other devices via the microUSB port. Up to .9A, which is just under the "standard" USB spec.

EDIT: Will add further observations as replies.

Posted on Oct 15, 2013 9:39:34 AM PDT
Last edited by the author on Oct 15, 2013 9:44:12 AM PDT
The audio choices that Amazon made here are a little bit interesting, because they inherited a particularly decent high fidelity audio codec processor from the Qualcomm reference platform (the WCD9320) to mate to the DSP already onboard the Snapdragon 800 SoC, capable of outputting 24 bit audio @ 192khz, but then they use a ho-hum audio amp.

The result is an audio stream that in theory can match what a lot of desktops are putting out to thier ports, but with a signal level significantly behind those comparisons in quality.

I think they did this for two reasons: 1) cost, 2) direct input from the volume control means an easy to implement volume control. The downside is using a cheap part with 103 db S-n-R where higher end cards are hitting around 115 to 124.

You end up with something on the level just ahead of a Soundblaster Audigy SE in the desktop world, which was 24-bit@96khz with a 100 db SnR and behind the Audigy 2 ZS which offers 24-bit@192Khz with a 108 dB SnR.

Practical notes:
- In line with some prior discussions on audio quality, the physical hardware of the new HDX is akin to a gen 1 audigy card, but behind that of the "current" world of Xonar and / or later Audigy or USB DAC offerings.

- Those using high fidelity headphones can expect decent sound output, but may lag volume that is available from other vendors. As you go up in volume, sound isolation and coherence will not match better USB DACs, etc.

- Android actually has challenges fully supporting the lossless playback at 24/192. In the LG G2, LG actually did thier own pipeline update to make it possible to do high resolution audio consistent with what they could pipe to the headphone jack. We will have to find out if the HDX benefits from those same updates given the preponderance of LG parts in this tablet, hopefully the software optimizations could be used by Lab126 as well.

- Its worth noting that for Bluetooth audio, even the LG G2 downsampled the audio for output, I would expect even if Amazon benefited from LG's development work in the audio out to the headphones, bluetooth audio for the HDX would be no different.

Posted on Oct 15, 2013 9:53:01 AM PDT
The network implementation on the HDX is actually a budget chip selection, where Amazon incorporated the older and cheaper QCA6234 from Qualcomm. I am not entirely sure why they did that given the number of AC networks already out there -- and reasonable identical-package-size options from Qualcomm for more recent technology support.

My best guess is that they already had technical information from qualcomm that they could use for the 6234 implementation - this is another part that is absolutely identical to the "Dragonboard" APQ8074 reference design - so it made sense to put development time in form factor integration (e.g. configuring the board to fit the space available) rather than dealing with adding something like the QCA9862 or similar for 802.11ac support. Whenever you introduce a new chip like that, you also have to test it for thermal properties, hardware compatibility, and battery drain.

It's impossible to know if they ever even looked at alternatives in this area, it was likely more convenient to simply stick with the reference design -- EVEN IF that meant giving up the ability to support new-generation wireless technology for higher throughput to wireless networks.

Posted on Oct 15, 2013 10:03:01 AM PDT
Last edited by the author on Oct 15, 2013 10:04:49 AM PDT
The storage chip was a clear choice for coherence at each storage size from a single vendor and balancing cost. Toshiba's THGBMAG7A2JBAIR is essentially a mid-market NAND that gives up top end storage speed, and "intelligence" of the interface to keep costs down. The equivalent higher end storage option at this size would have been the THGBMAG7B2JBAIM at the same voltage and operating conditions, but would have required a little more surface area on the mainboard. Also of consideration, is whether the device would even have benefited. The other nice thing about Toshiba is the ability to source large numbers of these chips from a single vendor - with identical performance options available at 16, 32, and 64GB - exactly what Amazon was looking for.

Storage performance is just ok on the HDX according to arstechnica, and given these internals, its easy to understand why. Without knowing more definitely how they implemented the controller pipeline to the storage and having a chance to dig into more vendors' Snapdragon 800, its possible that the additional performance may not have even been detectable.

Practical considerations:
- The storage performance of the HDX is akin to what you might see plugging a middle-market thumb drive into a recent laptop or desktop, and moving files back and forth.

- The only real drawback here comes in games that may be pre-loaded on the tablet. As some graphical titles start including high end textures and modelling assets, these data intensive read/writes are going to take just a touch longer.

- Outside of gaming, the practical limitations of tasks on the platform, and speed on your wireless connection means you would have to have inbound internet connections in excess of 160Mbps or so before your storage medium would be the limiting factor in how quickly you could download - say an amazon prime instant movie.

Posted on Oct 16, 2013 1:16:56 AM PDT
Dragi Raos says:
Interesting - thanks!
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Discussion in:  Kindle forum
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Total posts:  5
Initial post:  Oct 15, 2013
Latest post:  Oct 16, 2013

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